TiB₂ as a diffusion barrier for Cu/〈Si〉 metallization

TiB₂ films deposited by co-sputtering from a boron and a TiB₂ target are evaluated as the diffusion barrier for Cu metallization. Material characteristics of the TiB₂ films and metallurgical interactions of the Cu/TiB₂/〈Si〉 system annealed at 400-700°C for 30 min, in a 80%Ar+20%H₂ flow, were investigated by glancing angle X-ray diffraction, Auger electron spectroscopy (AES), and scanning electron microscopy (SEM). Sheet resistance was measured for electrical characterization. The composition and resistivity of the sputtered TiB₂ films varied with the bias applied on the substrate. To obtain a low film resistivity, a negative bias of 200V was applied during sputtering. The resulting TiB₂ film is nanocrystalline with a resistivity of 300 μΩcm. After copper deposition, the Cu/TiB₂/〈Si〉 samples have a constant sheet resistance after annealing up to 600°C for 30min. The overall sheet resistance of the sample increases by five orders of magnitude after annealing at 700°C, and scanning electron micrographs reveal that the sample surface is severely deteriorated after annealing at 700°C.